Selecting system



June 6, 1944. N, 1. HALL 2,350,888

S-ELECTING'SYSTEM Filed Nov. 21. 1941 2 Sheets-Sheet 2 IN [/5 N TOR N. HALL BY MW i I rog/1 Patented June 6, 1944 UNITED STATES PATENT orrlcs SELECTING SYSTEM Nathan I. Hall, Morristown, N. 1., assiznor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation or New York Application November 21, 1941, Serial No. 419,879

Claims. (01. 315-294) ins discharge tubes in which ionization occurs in stages and to efiect the selection of one of these relays and the exclusion of others after ionization of the corresponding tube has progressed through one or more of its stages.

Other objects of the invention are to simplify, to increase the speed of operation, and otherwise to improve selecting and controlling systems.

These objects are realized by means of a selecting and lock-out system in which a plurailty of lines, circuits, relays, or equivalent electrical devices, from which selection is to be made, are

provided with a plurality of discharge tubes, I

one for each of the several circuits or devices, together with means for causing the ionization of the tubes at random; in which the initial starting voltage applied to any tube causes the tube to ionize in two or more successive stages, each stage involving a ditlerent pair of tube electrodes; and in which the current flowing through a common impedance in response to the ionization in one of these stages in a particular tube alters the voltage applied to the remaining tubes sufllicently to render them inoperative; More specifically these selecting tubes are provided with a multiplicity of electrodes, each tube having a main anode, a main cathode, and two or I more auxiliary electrodes. If starting voltage is applied to the auxiliary electrodes of a plurality of these tubes simultaneously, initial ionization occurs in each tube, following which ionization transfers to the gap formed by one of the main electrodes and one of the auxiliary electrodes. The circuit for applying voltage to this gap includes a common impedance, and the current flowing therein as a result of the transfer of ionization in a particular tube lowers the voltage applied to the corresponding gaps of all other tubes to prevent the succesfuil transfer of ionization in any one of these other tubes. Hence one tube alone succeds in maintaining its transferred ionization. and this particular tube then proceeds to ionize its main gap, including the main anode and cathode, whereas the remaining tubes are rendered inoperative.

. A feature of the invention is a selecting system of the kind above-described in which the initial ionization of the tube is transferred 'in two successive stages, both stages involving ionization gaps formed by diflerent pairs of electrodes, and in which an exclusion or lock-out voltage is produced in each 01' these stages to render all except a particular one of the tubes inoperative.

These and other features of the invention will be described more fully in the following speciflcation. iIn the drawings accompanying the specificaton: I

Fig. 1 illustrates an embodiment of the invention in which dischargetubes 01' the screen grid type are employed;

Fig. 2 illustrates a second embodiment in which the tubes are provided with auxiliary anodes;

Figs. 3 and 4 show alternatives in which the tubes are provided with separate starting gaps; and

Fig. 5 shows an embodiment in which the tubes are provided with screen grids" and with separate starting gaps.

This invention is applicable to a wide variety of uses and to numerous kinds of systems. More specifically it is particularly useful wherever it is desirable to make a single exclusive random selection from a plurality of equivalent choices which are subject to a plurality of simultaneous demands. For example, in automatic telephone systems, and especially those of the crossbar type, there are numerous situations in which a plurality of demands may exist concurrently for an idle one of a group of lines, links, trunks, relays, magnets or other equivalent devices, whereas it is necessary to restrict the selection to a single 'one of these elements and to exclude all others either so long as the selected element is in use or temporarily until the necessary operations have been eflected to permit the selection of .second one of the desired elements or the group. A better understanding of the problems which make this exclusive method of selection so desirable in systems of the crossbar type may be had from a study of the circuit operations involvedln the patent to Carpenter, No. 2,235,803 of March 18, 1941, and in the patent to Busch et 2.1. 2,224,251 of December 10, 1940; However, as above-noted, the invention is not limited to telephone systems but may be applied to other types of communication systems and to any other systems where it may be found useful.

The selecting system illustrated in Fig. 1 com- 2 assasea it will be understood that the series may contain 5 as many as desired and that the controlling circuits are so arranged that attempts may be made to seize and operate the relays at random. Since the relays are subjected to random seizure;

it follows that frequently attempts will be made to seize two or more relays simultaneously. Under such conditions the associated tubes serve to limit the selection to a single relay and to guard the remaining relays of the series against simultaneous operation.

The associated discharge tubes I02, I02 are provided with main anodes, main cathodes and starting electrodes and screen grid electrodes. For example, tube I02 has a main anode I04, a

main cathode I05, a starting electrode I00 and a screen grid electrode I01. Similarly the tube I03 has a main anode I00, a main cathode I00, a starting electrode I I0 and a screen grid electrode III. The respective relays I00, IOI, etc., are

connected to the main anodes of the associated tubes and to the positivepole of anode battery H2. The main cathodes I05, I00 are connected directly in multiple to each other and thence through a common inductance element H0 and through a common resistor I I4 to ground. The.

starting electrodes are connected through individual resistors to the contacts of switches or. relays by means of which starting potential is applied at will to these electrodes. For instance,

starting electrode I05 is connected through resistor II5 to the switch IIS, which serves to connect the positive pole of battery II1 to the electrode. Similarly, starting electrode H0 is connected through resistor IIO to the individual switch H9. The screen grld's I01, III, etc., are :0

all connected directly in multiple with each other and thence through a common resistor I20 to the positive pole of the anode battery II2.

A description of the selection system of Fig. 1

will now be given. Assume that all of the relays is in the series are idle and that it is desired to select and operate the relay I00 to the exclusion of the others. To this end the common switch I2I is closed, followed by the closure of the individual switch II5. switches establishes the following circuit for the starting gap I05--I00: positive pole of battery II1, switch I2I, switch Ill, resistor II5, startingelectrode I05, cathode I05, inductive impedance II3, resistor II4 to ground and thence to the resistor I20, screen grid I01, cathode I05,

impedance element H0 and resistor II4 to ground. Thereupon the ionization within the tube immediately transfers to the main anode I04, and the main discharge circuit is now closed for the flow of current from the positive pole of battery II2 through the winding of relay I00, anode I04, cathode I05 and thence to ground. Relay I00 operates in this circuit and performs its related functions.

The closure of these '50 60 and the tube I00 remains inoperative.

anode-cathode circuit in the tube I02, the voltage drop across the common elements II 0 and H4, due to this current flow, applies a positive potential to the cathode I00 and to the cathodes of the unoperated tubes in the series. This positive potential on the cathodes of these tubes re-.

duces below the ionizing value the voltage across their control gaps to prevent the subsequent operation of any one of these .tubes in response to the closure of the individual switches. Therefore, relay I00 remains operated, and it is impossible to operate any one of the remaining relays until the guarding potential is removed from the cathodes of the associated tubes. Following theoperation of the selected relay I00 the switches H0 and I2l or the switch IIO alone may be opened to remove the starting potential from the electrodes. When it is desired to restore the .relay I00, the anode-cathode discharge circuit is opened in any conventional manner to permit the deionization of the main discharge gap of the tube I02.

Assume next that an attempt is made to seize and operate relays I00 and IOI simultaneously. That is to say, switch I2I is first closed and then switches H0 and H0 are closed at substantially the same time. In response to the closure of these switches, starting potential is applied to electrodes I08 and II 0, and the control gaps of both tubes I02 and I00 are ionized at the same time. Although the switches H0 and H9 may be -closed substantially at the sametime,

\ the speed with which the discharge tubes ionize their control gaps and transfer their ionizations is so great that one or the other of any pair of tubes undergoing simultaneous seizure will in all probability transfer its ionization from the main cathode to the screen grid somewhat in advance of the other tube. Assume, therefore, that while the tubes I02 and I03 ionize their control gaps concurrently, the transfer of ionization from the main cathode to the screen rid in the tube I02 precedes the corresponding ransfer in the tube I03. The instant the transfer takes place current flows from the battery I I2, common resistor I20, across the gap from screen grid I01 to cathode I05 through the common inductance H3 and resistance II4. This flow of current in the inductance III sets up a relatively high potential which, in addition to the drop across resistor I I4, is immediately applied to the cathode I09. Also the current flowing in resistor I20 lowers the positive potential on scream III. Thus the simultaneous reduction of the negative potential of cathode I00 and the positive potential of screen grid II I lowers the voltage between the cathode I00 and the screen grid III below the ionizing value. Therefore, the ionization fails to transfer from the cathode I00 to the screen grid III, As above explained, the ionization in the selected tube I03 continues its transfer to the main anode I04, and the desired relay I00 is operated. Similarly if three or more tubes are undergoing simultaneous attempts at seizure, the first one to transfer its ionization from the main cathode to thescreen grid will cause an induced voltage in the common impedance II3 which will lower the potential of the cathodes of the remaining tubes to prevent any one of them from transferring its ionization.

It will be noted that the blocking or lock-out potential produced inthe common impedance element H3 is applied directly to the cathodes During the time current is flowing in the main of all tubes which are to be prevented from op- The relays 200, L

battery 202 and the main anodes 200, 204 of'the respective tubes 205, 200. The main cathodes oi the tubes are connected through common impedance 201 and common resistor 200 to ground; and the starting electrodes 200, 2|. are connected through individual resistances and switches 2, 2|! and 2i: to the positive pole of battery 2. The auxiliary anodes M5. 2", which replace the screen grids of Fig. 1, are connected directly in multiple with each other and thence through the common resistor 2l.'| to the positive pole of battery 202.

To select one of the relays in Fig. 2; one or more of the corresponding starting switches are closed to cause the ionization of the starting gaps formed by the starting electrodes 200, 2" and the main cathodes 2H, 2l9.. Immediately following the ionization of the control gap or any tube the ionization transfers from the main cathode to the auxiliary anode, and the first tube to transfer its ionization sets up voltages across the impedance 201 and resistor 2'" which apply potentials to the cathodes and to the auxiliary anodes respectively of the remaining tubes to prevent a second one from transferring its ionization. If, for example, the tube 205 is the first one to transfer its ionization from the main cathode 2 to the auxiliary anode 2l5, current immediately flows from the positive pole of battery 202 through the common resistor 2H, auxiliary anode 2|5, cathode 2l8, impedance 201 and resistance 208 to ground. The voltage induced by the impedance 201 and also by resistance 200 is applied to the cathode 2 l0 and to the cathodes of all other tubes in the series and the drop across resistor 2|! is applied to the axillary anodes to prevent any other tube from transferring its ionization from the control gap to the gap formed by the main cathode and the auxiliary anode. Thereafter the preferred tube 205 transfers its ionization from the main cathode 2" to the anode 203, and current npw flows in the main discharge gap including the relay 200. Relay 200 operates and performs its required functions. I

In Fig. 3 the tubes 300, 30l have starting gaps, separate from the main anodes and cathodes. For example, the tube 300 has a main anode 002, a main cathode 303, and a starting gap formed by the starting anode 304 and the starting cathode 305. The starting anodes 304, 000 of all tubes are connected directly in m ultiple and thence through the common switch 301 and common resistor 300 to the positive pole of battery 309. The starting cathodes'305, 3|. are connected through individual resistors 3, M2 to the negative pole of battery. 1

When it is desired to select an idle one of the relays 3l3, 3 associated with the tubes 300, 30L the switch 301 is closed to apply starting potential tothe starting anodes 304, 305, etc., of all tubes in the series. The starting cathodes of all tubes corresponding to "busy relays will have ground potential applied thereto over conductors 315, 3H5, etc., whereas the starting cathodes corresponding to idle relays will be connected only to the negative pole of battery. Hence the starting gaps-of all tubes corresponding to idle relays ionize, and the gaps of the remaining tubes remain deionized. As soon as the starting gaps have ionized. ionization transfers'from the starting anodes to the main cathodes, and the first tube to transferits ionization sets up a voltage acm the common impedance 3" and a voltage across the common resistor 000 which locks out the other tubes. If, for example, it is assumed that the tube 000 first transfers its ionization from the starting anode 004 to the main cathode 003, the remaining tubes are excluded, and the ionization of tube 000 immediately transfers again to the main anode 002. Current now flows in the main discharge circuit from the grounded or positive pole of battery Ill through the common winding of relay 3", anode 002, cathode I03, inductance 3H, resistor 3|! to the negative pole of battery 0".

In Fig. 4 the tubes 400, 40L etc., are provided with separate starting gaps as in Fig. 3, but in this case the work relays 402, 403 are included in cir-" cuit with the main cathodes 000, 005. When it is desired to select one of the work relays, such as the relay 002, the individual switch 406 is closed to apply starting potential to the starting anode Ill. The starting or control gap l0|'l00 is ionized over a circuit traceable from the positive pole of battery 409, switch 006, resistor 0 10, starting anode 001, starting cathode 408, inductance ll I, resistor-H2 to the negative pole of battery 0. As soon as the starting gap 001-408 ionize, ionization transfers from the starting cathode 400 to the main anode. "0. This transferred ionization causes the flow of current from the positive pole of battery 5-, common resistor H6, anode 4, starting cathode 008, inductance 0| I, reiistor 2 to the negative pole of battery I. The voltage set up by the impedance I is applied to the starting cathode M! of tube 00! and to the starting cathodes of all other tubes and the drop across resistor 5 is applied to the main anodes to prevent any one of these tubes from transferring its ionization from the starting cathode to th'e'main anode thereof. Following the transfer of ionization from the starting cathode 000 to the main anode 4, the main discharge gap of the tube. ionizes, and current now flow in the main discharge circuit from battery 5, resistor l5, anode 4H, cathode 404, relay 402 to the negative pole of battery 8. If

it is desired to render any one of the work relays screen grids and with separate control gaps. Two successive transfers are made between the ionization of the control gap and the ionization of the main gap, and the lock-out feature is applied to both of these transfer operations. For

example, tub 500 is provided with a main anode- 5", a main cathode 502, a screen grid 503 and, a separate control gap formed by the starting anode 504 and a starting cathode 505. Similarly.

the tube 500 is provided with a main anode 501, a

main cathode 500, a screen grid 509 and with a.

separat control gap comprising the starting anode 5l0 and the starting cathode 5! I.

Whenit is desired to select the relay5l2 to the exclusion of other relays, the individual switch 5|! is closed to apply starting voltage to now flows from positivepole of battery 5 2,ato,aas

' tubesto render inoperative all tubes except said through common resistor iii, starting anode 5,

cathode 502 through the common resistor ill! to the negative pole of battery 5". The voltage drop produced across the common resistors H5 and SIS lowers the voltage across the corresponding gap of any other tube, such as tube 506. Any other tube, therefore, which has its control gap ionized simultaneously with the control gap of tube 500 and which does not transfer its ionization to the gap formed by the starting anode and the main cathode prior to the transfer by the tube 500, is locked out and prevented from establishing an ionization across the gap of the starting anode and main cathode. Immediately following the first transfer in the tube 500 a second transfer of ionization takes place between the main cathode 502 and the screen grid 503; As soon as this gap ionizes, current flows from the positive or grounded pole of battery 5", common resistor 5l8, screen grid 503, cathode 502, resistor ii! to the negative pole of battery 5". Current flowing in the common resistors SIB and H8 lowers the voltage across the gaps formed by the screen grid and the main cathode of all other tubes to prevent the transfer of ionization in any tube which may already have achieved ionization between it start anode and main cathode. Thus the tube 500 succeeds in locking out any other tube; in the second stage of ionization which may not have been successfully locked out in the first stage of ionization transfer. Immediately thereafter the final transfer takes place in the tube 500 between the main anode and cathode, and current now flows from the grounded pole of battery 5|! through the winding of relay 512, anode 5M, cathode 502, resistor SIG to the negative pole of battery 5". Relay 5|! operates, and the voltage drop acros the common resistor SIB prevents any other tube from ionizing its main discharge gap. Thereafter the switch 5" may be opened to deionize the control gap SIM-SIS. The relay 5|! may be released by opening the common anode supply circuit in any suitable manner.

While the space discharge tubes illustrated herein may be of any suitable type, such as those filled with diiierent gases, it has been found that better results are obtained in the systems disclosed when tubes filled with argon are employed.

What is claimed is:

1. In combination, a plurality of discharge tubes, each having main electrodes forming a main discharge gap and a plurality of auxiliary electrodes, circuit means for applying at random a starting potential to one of the auxiliary electrodes of one or more of said tubes to start the ionization of said tubes, an auxiliary discharge circuit common to all of said tubes and including an auxiliary gap of each tube formed by one of the main electrodes and one of the auxiliary electrodes, means for causing the transfer of ionization of any particular one of said tubes to the auxiliary gap thereof and the consequent flow of current in said auxiliary discharge circuit, and a common impedance element for producing a voltage drop in response to the flow of current in said auxiliary discharge "circuit, said voltage drop being applied to the auxiliary gaps of said particular tube.

2. In combinatiom ,a plurality of discharge tubes, each having main electrodes forming a main discharge gapand a plurality of auxiliary electrodes, circuit means for applying at random a starting potential to one of the auxiliary electrodes of each of a plurality of said tubes to start the ionization thereof, an auxiliary discharge circuit having a common branch for all of said tubes' and an individual branch for each tube including an auxiliary gap of such tube formed by one of the main electrodes and one of said auxiliary electrodes, potential means for causing the initial ionization of any particular one of said tubes to transfer to the auxiliary gap thereof and the consequent flow of current in the main branch of said discharge circuit, a common impedance element in the main branch of said circuit for pro-.- ducing a voltage drop in response to the flow of current in said auxiliary circuit, said voltage drop beingtapplied to the auxiliary gaps of said tubes to prevent the transfer of ionization of all tubes except said particular tube, a main discharge circuit for each of said tubes including the main electrodes thereof, and means responsive to the ionization of the auxiliary gap of said particular tube for causing the transfer of said ionization to the main gap of said tube and the consequent flow of current in the circuit of said main gap.

3. In combination, a plurality of discharge tubes, each having a main anode and a main cathode forming a main discharge gap and having auxiliary electrodes, circuit means for applying a starting voltage to the gaps formed by two of the electrodes of each of a plurality of said tubes for starting the initial ionization of said tubes simultaneously, a discharge circuit including a common branch, individual branches connecting said common branch in multiple to one of the main electrodes of each of said tubes, and individual branches connecting said common branch in multiple to one of the auxiliary electrodes of each of said tubes, the multipled main electrodes and the multipled auxiliary electrodes forming auxiliary discharge gaps, potential means responsive to the initial ionization of any particular one of said tubes'for causing the ionization of the auxiliary discharge gap of said tube, a common impedance element in the main branch of said discharge circuit for producing a voltage drop in response to the ionization of the auxiliary gap of said particular tube, said voltage drop serving to render inoperative all tubesexcept said particular tube, a main discharge circuit for each tube including the main discharge gap thereof, and means responsive to the ionization of the auxiliary discharge gap of said particular tube for causing the ionization of the main gap of said 4. In combination, a plurality of discharge tubes, each having two main electrodes formin a main discharge gap and having a plurality of auxiliary electrodes, circuitmeans for applying potential to one of the auxiliary electrodes of said tubes to cause the initial ionization of a plurality of said tubes simultaneously, a first auxiliary discharge circuit including a first auxiliary discharge gap of each of said tubes formed by one of the main electrodes and one of the auxiliary elecof said tubes formed by one of said main electrodes and another of said auxiliary electrodes, means responsive to the initial ionization of a particular one oi said tubes for causing the transfer of ionization in successive steps first to said first auxiliary gap and then to said second auxiliary gap of said particular tube, the ionization of each auxiliary gap causing the flow of current in the corresponding auxiliary discharge circuit, an impedance element common to both auxiliary discharge circuits, said impedance element serving to produce a voltage in response to the flow of current in the first auxiliary circuit to prevent the transfer of ionization to the first auxiliary discharge gap of all tubes except said particular tube, said impedance element serving to produce a voltage in response to theflow of current in said second auxiliary discharge circuit to prevent transfer of ionization to the second auxiliary gap of all tubes except said particular tube,

a main discharge circuit for each of said tubes including, the main discharge gap thereof, and means for causing the transfer of ionization from the second'auxiliary discharge gap of said particular tube to the main discharge gap thereof.

5. In combination, a plurality of discharge to start the ionization thereof, an auxiliary dis-'v charge circuit common to all of said tubes and including the auxiliary gap of each tube, voltage means for causing the transfer of the initial ionization of any particular one of said tubes to the auxiliary discharge gap thereof and the consequent flow of current in said auxiliary discharge circuit, and a common impedance element for producing a voltage drop in response to the flow of current in said auxiliary discharge circuit, said voltage drop being applied to the auxiliary gaps of said tubes to render all tubes inoperative except said particular tube.

' NATHAN I. HALL. 

